The present invention is generally related to sensing methods and systems. The present invention is additionally related to sensors utilized in automotive and mechanical applications. The present invention is also related to Hall and magnetoresistive (MR) sensor applications. The present invention is additionally related to position sensing methods and systems thereof.
Various sensors are known in the magnetic-effect sensing arts. Examples of common magnetic-effect sensors include Hall effect and magnetoresistive technologies. Such magnetic sensors can generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing by the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by subsequent electronics to yield sensing and control information. The subsequent electronics may be located either onboard or outboard of the sensor package.
Many automotive electronic systems make use of position sensors. When position sensors for automotive electronic systems were originally conceived and developed, such sensors were primarily utilized for the determination of clutch pedal and shift lever positions in automobile transmission applications. Reasonably accurate linear position sensing was required to identify the positions of the clutch pedal and the shift lever, using electrical signals from a non-contacting sensor approach. For example, in automated manual transmission applications, two sensors may be required to sense the shift lever position as it moves in an H-pattern from Reverse to Low to Second to Third gear. For a standard automatic transmission application, where the shift lever moves along a single axis direction, one position sensor may be required to sense whether the shift lever is in one of the gear operating positions (e.g., Reverse, Neutral, Drive, Low, etc.) as well as positions between such operating conditions.
Many of the sensors utilized in automotive applications are configured as position sensors, which provide feedback to a control unit. Many of these types of sensors and related systems are mechanical in nature and are very sensitive to the wearing of contacts, contact contamination, and so forth. To help solve many of the warranty problems associated with mechanical sensors, designers have searched for non-contacting electrical solutions provided by magnetoresistive and/or Hall-effect technologies, which have attempted to detect variance in a magnetic field. One of the primary problems with this approach is the inability of such systems to accurately detect position. The accuracy requirement of such systems makes it difficult, for example, to use a single Hall element because of the offset and shifts over temperature.
The difficulty with both Hall and magnetoresistive technologies is that high accuracy switching points at low and high RPM""s are difficult to achieve. Positions sensors must meet high repeatability requirements for both camshaft and crankshaft applications in automotive devices. The present inventor has thus concluded that a need exists for an improved sensing method and system that can provide high accuracy and highly repeatable switch points through a complete RPM range. The present invention is therefore directed toward improved magnetic sensing methods and systems.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the present invention to provide an improved sensor method and system.
It is another aspect of the present invention to provide for a sensing method and system that utilizes a Hall and/or magnetoresistive sensor.
It is yet another aspect of the present invention to provide for a peak detector circuit.
It is still another aspect of the present invention to provide for a filter averaging circuit.
It is also an aspect of the present invention to provide for a camshaft and/or crankshaft position sensor.
The aforementioned aspects of the invention and other objectives and advantages can now be achieved as is now summarized. Magnetic sensing methods and system are disclosed herein. A minimum magnetic signal output and a maximum magnetic signal output can be detected utilizing a sensor comprising a peak detector circuit associated with a filter averaging circuit and one or more magnetic elements (e.g., a Hall element and/or magnetoresistive bridge). An average magnetic signal output can then be determined utilizing the filter averaging circuit when a target begins to rotate in front of the sensor. A minimum magnetic signal output and a maximum magnetic signal output can be detected utilizing a sensor that includes a peak detector circuit, a filter averaging circuit and one or more magnetic elements (e.g., a Hall element and/or magnetoresistive bridge). An average magnetic signal output can then be determined utilizing the filter averaging circuit when a target begins to rotate in front of the sensor.
The filter averaging circuit stabilizes when an area of a curve above the average magnetic signal output is equal to an area under the curve. The sensor can be automatically switched from a peak detector circuit mode to a filter averaging circuit mode at a specified frequency. A sensor switching level can be established approximately halfway between the minimum magnetic signal output and the maximum magnetic signal output. The peak detector can be coupled to one or more biasing magnets. The sensor itself can function as, for example, a camshaft position sensor and/or a crankshaft position sensor.